The present invention generally relates to marine seismic prospecting, and in particular to seismic prospecting methods using multiple vessels.
Petrochemical products such as oil and gas are ubiquitous in society and can be found in everything from gasoline to children's toys. Because of this, the demand for oil and gas remains high. In order to meet this high demand, it is important to locate oil and gas reserves in the Earth. Scientists and engineers conduct “surveys” utilizing, among other things, seismic and other wave exploration techniques to find oil and gas reservoirs within the Earth. These seismic exploration techniques often include controlling the emission of seismic energy into the Earth with a seismic source of energy (e.g., dynamite, air guns, vibrators, etc.), and monitoring the Earth's response to the seismic source with one or more receivers in order to create an image of the subsurface of the Earth.
Each receiver may include, for example, a pressure sensor and/or a particle motion sensor in proximity to one another. The pressure sensor may be, for example, a hydrophone that records scalar pressure measurements of a seismic wavefield. The particle motion sensor may be, for example, a three-component geophone that records vectorial velocity measurements of the seismic wavefield. By observing the reflected seismic wavefield detected by the receiver(s) during the survey, the geophysical data pertaining to reflected signals may be acquired and these signals may be used to form an image indicating the composition of the Earth near the survey location.
Marine seismic surveys generally involve towing one or more streamer cables comprising a plurality of receivers with a seismic vessel. The number of receivers placed in the streamer and the relative distance between the receivers generally determines the quality of seismic data that is recorded. Improving seismic data collection has traditionally involved increasing the length of streamer cables and the density of receivers included therein. However, the longer the streamer cables, the more difficult it becomes to keep streamer cables separated and in a desired configuration, for example, when turning the seismic vessel or maneuvering the seismic vessel in icy or obstructed waters.